This invention relates to carburetor control devices, and in particular is intended to be used in conjunction with a carburetor for an internal combustion engine to provide the dual functions of controlling throttle closure rate after removal of an operator input command so that the carburetor throttle slowly returns to a curb idle setting, and for permitting the throttle to close to a setting below its curb idle setting upon de-energization of the ignition system for the internal combustion engine.
The prior art reveals a number of devices which function to slow throttle movement during the transition from a run condition to a curb idle condition of an internal combustion engine. These devices are known in the art, and are defined for the purposes of this specification, as a "dash pot". In general, a dash pot is a diaphragm valve device which includes a shaft extending outwardly from a diaphragm valve housing. The diaphragm valve is arranged so that it is capable of reciprocal movement between first and second positions. In a first direction of movement, the action of the diaphragm valve offers increased resistance to shaft movement, so that the shaft moves between the first and second positions slowly. In internal combustion engines, this action is applied to the throttle of the carburetor so that removal of an operator input command, for example, by removing pressure on the accelerator pedal of a conventional passenger vehicle, causes some linkage for controlling throttle movement to bear against the dash pot shaft. The diaphragm valve of the dash pot offers resistance to shaft movement so that the throttle returns to its curb idle position at a controlled rate. A controlled return to the curb idle is important in meeting emission standards for exhaust gases of the internal combustion engine. A spring commonly is provided on one side of the diaphragm which is compressed at the curb idle position. The spring returns the diaphragm and its associated shaft to its initial position upon a command for increased acceleration. The shaft then is able to re-engage the throttle or throttle linkage upon removal of the succeeding operator command.
The prior art also reveals solenoid actuated devices which set the curb idle position-of-the carburetor. In general, these devices include a solenoid energized by the vehicle ignition system so that a second shaft is positioned to engage a suitable throttle linkage at the curb idle position of the carburetor. Upon de-energization of the solenoid, the second shaft retracts so that the throttle is permitted to move to a position below the curb idle setting. Internal combustion engines finding application in present-day passenger vehicles, for example, tend to operate at higher curb idle speeds than older models of those vehicles. When the ignition system is de-energized at the high r.p.m. curb idle speeds, the internal combustion engine has a tendency to continue to draw air and fuel through the carburetor so that the engine exhibits what is known in the art and for the purposes of this specification as after run, in that the engine continues to operate in a manner similar to a diesel engine. Use of solenoid operated devices to permit throttle closure below the curb idle position prevents the occurrence of the after run condition.
While these prior art devices work well for their intended purposes, as a class they have been characterized by relatively expensive constructions. In addition, the use of separate devices has required the use of valuable space in the engine compartment, when space is at a premium as vehicle manufacturers continually attempt to reduce automobile size.
The invention described hereinafter provides the dual function of controlled throttle release and after run prevention by providing a single unit for accomplishing these functions. The device itself is simpler in construction and lower in cost than designs now used for that purpose.
One of the objects of this invention is to provide a simplified structure for providing controlled throttle release and preventing engine after run.
Another object of this invention is to provide an integrally constructed unit providing the dual functions of throttle control and after run prevention.
Yet another object of this invention is to provide a dual function device utilizing a single shaft assembly for dual function operation.
Still another object of this invention is to provide a diaphragm assembly having internal valve means for enhancing diaphragm movement between a first position and a second position.
Yet another object of this invention is to provide a unitary device for providing controlled throttle release and preventing engine after run which permits easy adjustment of the curb idle position of an internal combustion engine.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.